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First Law of Thermodynamics.

From the circumferences of F F weights G G were hung, %% !
being allowed to fall, rotated the paddles and raised tb«-* !
perature of the water. By repetition, the temperature * ^ r
water was raised to a measurable quantity, the work of the ** H
weights being simultaneously noted, until the average of f Sl
experiments gave the ' mechanical equivalent' as 772 foot 11 *'**
one British Thermal Unit. We may now state the
First Law of Thermodynamics. — Heat
energy are mutually convertible, and Joule's equivalent (f)
rate of exchange. (See pp. 930 and 1130.)

Internal and External Work during Evapormfci

—In heating water and evaporating it:

i.—The temperature of the water has been raised.

2.—The water has been changed into steam at the    *;

3*—The volume of the water and steam has been

against external resistance.

* Rowland's later value, 778, is probably more nearly correct*